Blank material, method for press molding blank material, and press molding device

ABSTRACT

A molding recessed part of a lower mold constituting a press molding device is provided with a first blank holder, and a circular second blank holder is freely movably provided on one outer peripheral side of the first blank holder. Meanwhile, of first and second blank holes opened in blank material, straight-line parts of the second blank hole have formed therein a pair of tensile force adjusting parts, and arched parts of first and second opening parts are mounted on the second blank holder. Furthermore, when draw forming of the blank material is performed, the tensile force imparted to the straight-line parts to the outside is adjusted by the tensile force adjusting parts, and the tensile force imparted to the arched parts to the outside in the radial direction is adjusted by the second blank holder.

TECHNICAL FIELD

The present invention relates to a blank material including an openingpart, and a press forming method and a press forming device forperforming draw forming for the blank material (a blank material, amethod for press molding the blank material, and a press moldingdevice).

BACKGROUND ART

A side panel of an automobile is conventionally manufactured by, forexample, performing press-forming of a metal plate material, and thisside panel is formed by deep draw forming. The whole periphery of theside panel that is formed in advance and the whole periphery of the edgepart of an opening part that is formed in advance similarly are held bya blank holder, so that the deep draw forming is performed.

In recent years, it has been known that an upper part of a rear wheelarch in the side panel is formed such that the upper part has a moreconvex shape by the deep draw forming, for example, in order to improvethe design of the automobile. When this side panel is formed from asingle sheet of plate material by the deep draw forming, a wrinkle orwrinkles occur easily and tension is required particularly in a straightline part that is close to the convex shape of the upper part of therear wheel arch of the opening part for a rear door that is formed inadvance on the side of the rear wheel arch because inflow of thematerial to the convex shape of the upper part of the rear wheel arch islarge in the forming.

Moreover, in the opening part for the rear door, an R part in an up-downdirection is extended due to the inflow of the material and easilycracks. Thus, it is required that an extending amount of the material issmall. Therefore, it is necessary to deal with the R part and thestraight line part differently in the opening part. Note that the rearwheel arch and the side panel may be formed separately and connected bywelding, for example; however, it is a problem that the manufacturingprocess is increased and the manufacturing cost is also increased inthis case.

For example, in a press forming method disclosed in Japanese Patent No.3814711, when a concave part is formed from a metal plate material, aslit is formed in advance along the whole inner periphery of a part tobecome a scrap in a formed article. Thus, force acts on only the outsideof the slit in draw forming, so that the forming can be performedwithout a crack or the like on an end part of the slit.

However, in the above press forming method, the draw forming isperformed to form the concave part such that a bead is disposed only onan inside part of a central part of one side of the part to become thescrap. Thus, it is difficult to apply tension on a straight line partwhere the tension is required.

Furthermore, in a press forming device disclosed in Japanese Laid-OpenUtility Model Publication No. 63-145519, a storage groove is formed at aposition that is near a blank holder disposed on an outer peripheralside in a punch corresponding to a lower die, and a floating punch isprovided to this storage groove so that the floating punch can movethrough a cylinder in the up-down direction. In a state where a work ismounted on an upper surface of the punch, a die descends from the upperside so that the outer edge part of the work is held by the die and theblank holder, the die descends further and is brought into contact withthe floating punch such that the work is held, and the draw forming isperformed for the work between the die and the lower die.

SUMMARY OF INVENTION

The present invention has been made in relation with the abovesuggestions, and an object is to provide a blank material, and a pressforming method and a press forming device for the blank material inwhich, in draw forming for the blank material including an opening part,a formed article with high quality can be obtained while a crack in theopening part is prevented.

In order to achieve the above object, the present invention provides ablank material for which draw forming is performed in a press formingdevice to make a body panel of an automobile, the blank materialincluding an opening part including arched parts provided in an up-downdirection of the body panel and connection parts each having anapproximately straight line shape provided in a front-rear direction ofthe body panel that is approximately orthogonal to the arched parts andconnected to the arched parts, wherein a tension adjusting part isprovided to the connection part, the tension adjusting part extending toan inside of the opening part and configured to adjust tension appliedoutwardly in forming.

According to the present invention, the blank material that is formed bythe draw forming in the press forming device includes the opening partincluding the arched parts provided in the up-down direction of the bodypanel and the connection parts with the approximately straight lineshape provided in the front-rear direction of the body panel andconnected to the arched parts, wherein the tension adjusting partsextending to the inside of the opening part are provided to theconnection parts and the tension applied to the connection partsoutwardly can be adjusted when the draw forming is performed.

Therefore, even when deep draw forming is performed for the blankmaterial including the opening part, inflow to the outside of theconnection parts with the approximately straight line shape is adjustedas appropriate with respect to the arched parts. Thus, a wrinkle at aformed part with a convex shape provided in the front-rear direction ofthe opening part is prevented, so that a formed article with highquality can be obtained.

Moreover, in order to prevent the wrinkle due to the inflow of amaterial to the convex shape of an upper part of a rear wheel arch inthe forming, the tension adjusting part may be formed for each of a pairof the connection parts. Thus, the tension can be applied by grippingthe tension adjusting part by (first and second) blank holders of thepress forming device, so that it is possible to prevent the wrinkle.

Furthermore, in order to prevent a crack due to the inflow of thematerial to the arched part (R part) in the opening part for a reardoor, each of the arched parts may be formed in a manner that the archedpart is smaller than a formed arched part of a formed body in which thearched part has been formed, and the arched part has a shape that isclose to the formed arched part. Thus, it is possible to prevent thecrack by reducing an extending amount of the material in the archedpart.

In addition, the present invention provides a press forming method inwhich draw forming is performed for a blank material including anopening part that includes arched parts and connection parts each havingan approximately straight line shape and connected to the arched parts,wherein an edge of the opening part is pressurized and held between anupper die and a first blank holder provided to a lower die, and thearched parts positioned outside a held part of the blank material heldbetween the upper die and the first blank holder is pressurized and heldbetween the upper die and a second blank holder provided outside thefirst blank holder.

According to the present invention, when the draw forming is performedfor the blank material including the opening part, the edge of theopening part is pressurized and held between the first blank holderprovided to the lower die and the upper die, and the arched parts of theopening part positioned outside the held part of the blank material heldbetween the first blank holder and the upper die is pressurized and heldbetween the second blank holder provided outside the first blank holderand the upper die.

Accordingly, the edge of the opening part can be held between the firstblank holder and the upper die, and at the same time, the arched partspositioned outside the held part can be held between the upper die andthe second blank holder provided outside the first blank holder.

As a result, since the opening part is formed such that the arched partsare positioned outside the first blank holder, the crack can beprevented by suppressing the inflow to the outside in the forming andthe draw forming can be performed for sure by the second blank holder.

Moreover, a bead may be formed by holding, between the upper die and thefirst blank holder, a tension adjusting part extending from theconnection part to an inside of the opening part. Thus, the tension canbe applied to the blank material more effectively.

In addition, the present invention provides a press forming deviceconfigured to perform draw forming for a blank material including anopening part that includes arched parts and connection parts each havingan approximately straight line shape and connected to the arched parts,the press forming device including: an upper die; a lower die disposedso as to face the upper die and including a mounting surface on whichthe blank material is mounted; a first blank holder disposed so as toface the upper die and configured to hold an edge of the opening part ofthe blank material with the upper die; and a second blank holderdisposed outside the first blank holder and configured to hold, betweenthe second blank holder and the upper die, the arched parts positionedoutside a held part of the blank material held between the first blankholder and the upper die, wherein the first blank holder and the upperdie include a bead configured to hold with pressure a tension adjustingpart extending from the connection part of the blank material to aninside.

According to the present invention, the press forming device thatperforms the draw forming for the blank material including the openingpart that includes the arched parts and the connection parts includesthe first blank holder that faces the upper die and holds the edge ofthe opening part in the blank material with the upper die, and thesecond blank holder that is positioned outside the first blank holder,wherein the second blank holder is provided such that the arched partspositioned outside the held part of the blank material held between thefirst blank holder and the upper die can be held between the secondblank holder and the upper die.

Accordingly, when the draw forming is performed for the blank material,the tension applied to the connection parts of the opening partoutwardly can be adjusted as appropriate by the bead of the tensionadjusting part and at the same time, the tension applied outwardly canbe adjusted by holding the arched parts through the second blank holder.

As a result, when the draw forming is performed for the blank materialincluding the opening part, both the tension adjustment for theconnection parts and the tension adjustment for the arched parts areperformed as appropriate at the same time. Here, the connection partscrack less easily even if the inflow of the blank material is large, andthe arched parts easily crack if the inflow is large. Thus, it ispossible to prevent the wrinkle in the edge of the connection parts andthe crack in the edge of the arched parts in the forming, so that theformed article with high quality in which the drawing is deep can beobtained.

Moreover, the second blank holder may have a circular shape. Thus, thetension adjusting part of the connection part is gripped by the secondblank holder. Therefore, the tension can be applied more effectively.

Furthermore, the bead may extend along a direction that is approximatelyorthogonal to an extending direction of the tension adjusting part.Thus, the tension can be applied equally to the blank material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a side outer panel for an automobile formed bya press forming device according to an embodiment of the presentinvention;

FIG. 2 is a front view expressing a blank material before the side outerpanel in FIG. 1 is formed;

FIG. 3 is a magnified plan view expressing the vicinity of a secondblank hole of the formed blank material;

FIG. 4 is a plan view of a lower die, and first and second blank holdersincluded in the press forming device;

FIG. 5 is a magnified plan view of a second holder part of the firstblank holder and the second blank holder in FIG. 4;

FIG. 6 is a cross-sectional view along a line VI-VI in FIG. 5;

FIG. 7 is a cross-sectional view along a line VII-VII in FIG. 5; and

FIG. 8A is a schematic diagram expressing change in a cross-sectionbefore and after a straight line part in FIG. 2 is formed, and FIG. 8Bis a schematic diagram that is used to compare an arched part in FIG. 2before forming and a formed arched part after the forming.

DESCRIPTION OF EMBODIMENT

A press forming device 10 is used to perform press forming of a blankmaterial 14. Here, a case where a side outer panel (body panel) 12 forautomobiles is formed from a steel plate corresponding to the blankmaterial 14 by using the press forming device 10 is described.

First, the side outer panel 12 corresponding to a formed article isdescribed with reference to FIG. 1. For example, this side outer panel12 constitutes a side part of a body of the automobile and includes afront pillar part 16 formed on a front side (arrow A direction) along avehicle direction, a rear pillar part 18 that is formed on a rear side(arrow B direction), a center pillar part 20 that is formed in anapproximately center part in the vehicle direction, a roof part 22 thatconnects upper ends of the front pillar part 16, the center pillar part20, and the rear pillar part 18, and a side sill part 24 that connectslower ends of the front pillar part 16, the center pillar part 20, andthe rear pillar part 18.

In the side outer panel 12, a first door opening part 26 that issurrounded by the front pillar part 16, the center pillar part 20, theroof part 22, and the side sill part 24 is formed, and a second dooropening part 28 that is surrounded by the center pillar part 20, therear pillar part 18, the roof part 22, and the side sill part 24 isformed. On a rear side of this second door opening part 28 (arrow Bdirection), a rear fender part 30 is formed at a position above a reartire that is not shown.

Next, the blank material 14 to be press-formed is described withreference to FIG. 2 and FIG. 3.

This blank material 14 is made of, for example, a steel plate withcertain plate thickness, and formed as a long piece along a front-reardirection of a vehicle (arrow A or B direction). In addition, the blankmaterial 14 includes a first blank hole 32 that is formed on one endside (arrow A direction) of the blank material 14 and serves as thefirst door opening part 26 of the formed article (side outer panel 12),and a second blank hole (opening part) 34 that is formed on the otherend side (arrow B direction) and serves as the second door opening part28 of the formed article. The first blank hole 32 and the second blankhole 34 are open while being separated from each other by apredetermined distance along the front-rear direction (arrow A or Bdirection) of the vehicle.

For example, the first blank hole 32 is formed such that thecross-sectional shape thereof is an approximately triangle shape, and onthe other hand, the second blank hole 34 is formed so as to have anapproximately oval shape which is elongate in an up-down direction(arrow C direction) that is approximately orthogonal to the front-reardirection of the blank material 14. This second blank hole 34 includes afirst opening part 36 and a second opening part 38 that are open at anupper part and a lower part each with a semicircular shape, a pair ofstraight line parts (connection parts) 40 a, 40 b that connects thefirst opening part 36 and the second opening part 38, and a pair oftension adjusting parts 42 a, 42 b extending from the straight lineparts 40 a, 40 b to the inside.

This first opening part 36 includes an arched part 44 a that is formedon an upper side and curves such that the cross-sectional shape thereofis arched toward the upper side, and the second opening part 38 includesan arched part 44 b that is formed on a lower side with respect to thefirst opening part 36 and curves such that the cross-section shapethereof is arched toward the lower side. As illustrated in FIG. 3, thearched parts 44 a, 44 b are formed so as to be positioned a little moreon the inside in a radial direction than a formed arched part 46 of theformed article after forming.

In other words, the arched parts 44 a, 44 b are formed such that theradius thereof is less than the radius of the formed arched part 46 ofthe formed article, and the arched part 44 a is close to the upperformed arched part 46 and the arched part 44 b is close to the lowerformed arched part 46.

That is to say, the second blank hole 34 is formed such that the firstopening part 36 and the second opening part 38 face each other in theup-down direction, the straight line part 40 a and the straight linepart 40 b are formed so as to face each other in the front-reardirection (arrow A or B direction) between the first and second openingparts 36, 38.

The straight line part 40 a connects one end part of the arched part 44a of the first opening part 36 and one end part of the arched part 44 bof the second opening part 38, and the straight line part 40 b connectsthe other end part of the arched part 44 a of the first opening part 36and the other end part of the arched part 44 b of the second openingpart 38.

The tension adjusting parts 42 a, 42 b respectively extend inward so asto be approximately orthogonal to the pair of straight line parts 40 a,40 b, are formed with a predetermined width in the up-down direction(arrow C direction), and protrude from the straight line parts 40 a, 40b by a predetermined length. In other words, the pair of tensionadjusting parts 42 a, 42 b extends so as to approach each other towardthe center of the second blank hole 34.

Next, the press forming device 10 that performs the press forming of theabove blank material 14 is described.

This press forming device 10 is used to perform what is called drawforming, and includes a lower die 48 as a forming die to perform a deepdrawing process for a work corresponding to the blank material 14, anupper die 50 that approaches or moves away from the lower die 48 underthe action of a lifting mechanism that is not shown, and first andsecond blank holders 52, 54 to hold the blank material 14 as illustratedin FIG. 4 to FIG. 7.

The lower die 48 is a fixed type that is fixed to a base or the likethat is not shown. An outer edge part 56 (see FIG. 6 and FIG. 7) of thelower die 48 has a convex shape and the lower die 48 includes a formingconcave part 58 with a concave shape on an approximately central part.The upper die 50 is a movable type that is displaceable in a verticaldirection (arrow D direction in FIG. 6 and FIG. 7) and includes aforming convex part 60 that can be inserted into the forming concavepart 58 of the lower die 48. On a lower surface of this forming convexpart 60, protruding parts 62 are formed at positions that face the topof the first blank holder 52.

When the upper die 50 and the lower die 48 are closed, the formingconvex part 60 of the upper die 50 is inserted into the forming concavepart 58 of the lower die 48. Thus, a cavity is formed so as to have theshape of the formed article (side outer panel 12) between the upper die50 and the lower die 48.

The first blank holder 52 is provided in the forming concave part 58 ofthe lower die 48 such that the first blank holder 52 can move in thevertical direction, and includes a first holder part 64 that forms theperiphery of the first blank hole 32 of the blank material 14 and asecond blank holder part 66 that forms the periphery of the second blankhole 34 of the blank material 14. The first and second holder parts 64,66 are formed so as to be separated from each other along the front-reardirection of the lower die 48 (arrow A direction) (see FIG. 4).

As illustrated in FIG. 6 and FIG. 7, the first and second holder parts64, 66 are supported by a plurality of cushion pins 68 whose lower endsextend from an energizing means that is not shown, and the first blankholder 52 including the first and second holder parts 64, 66 aredisplaced in accordance with forward (upward) or backward (downward)movement of the cushion pins 68 along the vertical direction (arrow Ddirection).

Moreover, the top of the first and second holder parts 64, 66 that facesthe upper die 50 has an approximately plane shape, and a circular groovepart 70 is formed near an outer edge part on the top of this firstholder part 64. On the other hand, on the top of the second holder part66, a pair of groove parts 72 extending in an approximately up-downdirection of the lower die 48 is formed. When the blank material 14 isformed between the upper die 50 and the first blank holder 52, theprotruding part 62 (see FIG. 6) of the upper die 50 is inserted into thecircular groove part 70 and the groove parts 72 in a state where theblank material 14 is held between the upper die 50 and the first blankholder 52. Thus, a bead 74 is formed in the blank material 14 near eachof the first and second blank holes 32, 34.

Note that the bead 74 formed by the first holder part 64 has a circularshape in accordance with the circular groove part 70, and the beads 74formed by the second holder part 66 has a straight line shape inaccordance with the pair of groove parts 72 (see FIG. 3).

The second blank holder 54 has a circular shape so as to surround thesecond holder part 66 in the first blank holder 52, a plurality ofcylinders 76 are provided below the second blank holder 54, and thesecond blank holder 54 is supported by a cylinder rod 78. A formingsurface 54 a of the second blank holder 54 that faces the upper die 50is formed so as to rise from the side of the first blank holder 52corresponding to the inside to the side of the lower die 48corresponding to the outside in the radial direction.

In accordance with forward (upward) or backward (downward) movement ofthe cylinder rod 78 of the cylinder 76, the second blank holder 54 movesforward/backward (upward/downward) with respect to the lower die 48 inthe vertical direction.

The press forming device 10 according to the embodiment of the presentinvention is basically structured as described above. Next, a method forforming the blank material 14 is described.

First, the blank material 14 is disposed between the lower die 48 andthe upper die 50 that are opened. At this time, the first and secondblank holders 52, 54 are positioned at a top dead center that is thehighest point of the first and second blank holders 52, 54 under theenergizing action of the cushion pin 68 and the cylinder 76,respectively. The first and second blank holders 52, 54 are mounted suchthat the blank material 14 is in contact with the top (mounting surface)of the first and second blank holders 52, 54.

The blank material 14 is mounted such that the first blank hole 32thereof faces the first holder part 64 of the first blank holder 52, thestraight line parts 40 a, 40 b and the tension adjusting parts 42 a, 42b of the second blank hole 34 face the second holder part 66, and thearched parts 44 a, 44 b of the first and second opening parts 36, 38face the second blank holder 54.

Then, in order to perform the press forming, the upper die 50 movesdownward to approach the lower die 48 under the driving action of thelifting mechanism that is not shown, and the forming convex part 60 ofthe upper die 50 is inserted into the forming concave part 58 of thelower die 48. Thus, first, the surface of the forming convex part 60that faces the first blank holder 52 touches and presses a part of theblank material 14 that is mounted on the first blank holder 52.

Therefore, the first blank holder 52 receives pressing power from theupper die 50 and descends while pressing down the cushion pin 68, andthe blank material 14 is pressed into the circular groove part 70 of thefirst holder part 64 by the protruding part 62 of the upper die 50 so asto be plastically deformed to have the bead 74 with the circular shape.At the same time, the tension adjusting parts 42 a, 42 b of the secondblank hole 34 are held between the upper die 50 and the top of thesecond holder part 66. Thus, as illustrated in FIG. 3, the two beads 74with the straight line shape that are depressed downward are formed inthe tension adjusting parts 42 a, 42 b. These beads 74 are formed alonga width direction of the tension adjusting parts 42 a, 42 bcorresponding to the up-down direction of the blank material 14.

When this upper die 50 has descended further, the draw forming isperformed between the outer edge part 56 of the forming convex part 60and an inner edge part of the forming concave part 58 in the verticaldirection (arrow D direction) as illustrated in FIG. 6. Accordingly, theinside of the blank material 14 is pulled by predetermined tensionoutwardly corresponding to the rear side of the vehicle (arrow Bdirection). At this time, the straight line parts 40 a, 40 b of thesecond blank hole 34 are adjusted by the tension adjusting parts 42 a,42 b held between the upper die 50 and the first blank holder 52 throughthe beads 74 such that the tension becomes predetermined tension.Accordingly, inflow of the blank material 14 in the front-rear direction(arrow A or B direction) of the vehicle is adjusted.

As illustrated in FIG. 8A, in the straight line parts 40 a, 40 b, adeformation amount in the vertical direction (arrow D direction) becomeslarge because of the upper die 50 and the lower die 48. However, sincethe inflow of the blank material 14 to the outside (arrow E direction)is large, a crack does not occur in the forming.

At the same time, along with the descent of the upper die 50, asillustrated in FIG. 7, the cylinder rod 78 of the cylinder 76 is presseddownward and the second blank holder 54 is pushed down through the blankmaterial 14, and the arched parts 44 a, 44 b of the first and secondopening parts 36, 38 of the second blank hole 34 are held andpressurized by the second blank holder 54 so that the draw forming isperformed on the forming surface 54 a.

In this case, as illustrated in FIG. 3, the arched parts 44 a, 44 b ofthe first and second opening parts 36, 38 of the second blank hole 34are formed, in advance, in the shape that is close to the formed archedpart 46 in the radial direction that has been formed. Thus, the inflowof the blank material 14 to the outside in the radial direction withrespect to the second blank hole 34 is small.

Here, in the aforementioned arched part 44 a of the second blank hole34, the variation of the inflow of the blank material 14 in the formingis described briefly with reference to FIG. 8B. Note that in FIG. 8B, apart of the arched part 44 a before the forming is regarded as a firstarched portion R1, and the formed arched part 46 in which the firstarched portion R1 is formed by the press forming is regarded as a secondarched portion R2.

As can be understood from FIG. 8B, the length of the first archedportion R1 corresponding to a part of the arched part 44 a is L1. Whenthe first arched portion R1 is formed, this part is pushed out andexpanded by a predetermined distance to the outside in the radialdirection and then, this part becomes the second arched portion R2 ofthe formed arched part 46 that has been formed. The length of the secondarched portion R2 is L2 that is longer than the length of the firstarched portion R1.

That is to say, if the inflow of the blank material 14 corresponding tothe push-out distance in the radial direction is F1, the differencebetween the length L2 of the second arched portion R2 after the formingand the length L1 of the first arched portion R1 before the forming isL2-L1.

On the other hand, for example, if a third arched portion R1′ before theforming (see dashed line in FIG. 8B) is set to a position that is moreon the inside than the first arched portion R1 in the radial directionsuch that the inflow of the blank material 14 to the outside in theradial direction with respect to the first arched portion R1 becomeslarge, inflow F2 (distance) that is larger than the above one isrequired in order to form the second arched portion R2 from the thirdarched portion R1′. In addition, the difference between the length L1′of the third arched portion R1′ and the length L2 of the second archedportion R2 after the forming is L2-L1′.

Thus, if the forming is performed by the amount of the inflow F2 inwhich the blank material 14 flows more largely to the outside in theradial direction, the difference from the length L2 of the second archedportion R2 increases for L1-L1′, compared with a case where the formingis performed by the amount of the inflow F1.

In this arched part 44 a, as illustrated in FIG. 8B, as the inflow ofthe blank material 14 to the outside in the radial direction is largerin the forming, the crack occurs more easily. Thus, it is preferablethat the shape of the arched portion before the forming be set such thatthe inflow is as small as possible with respect to the second archedportion R2 after the forming, that is, the separation distance in theradial direction is small.

Note that the arched part 44 a of the first opening part 36 is describedabove. Since the arched part 44 b of the second opening part 38 issimilar to the arched part 44 a of the first opening part 36, thedetailed description of the arched part 44 b of the second opening part38 is omitted.

As described above, when the blank material 14 is formed, the tension inthe front-rear direction of the vehicle is controlled by adjusting thetension to be applied to the straight line parts 40 a, 40 b of thesecond blank hole 34 by the tension adjusting parts 42 a, 42 b, and thetension in the up-down direction to be applied to the arched parts 44 a,44 b of the first and second opening parts 36, 38 is controlled by thesecond blank holder 54.

Note that each of the drawings (views) is simplified; however, athree-dimensional shape is formed on an inner edge of the second blankhole 34 of the blank material 14 in fact. In particular, as the formingprocess proceeds, tensile force toward the rear side (arrow B direction)acts on the straight line part 40 b corresponding to the rear side ofthe vehicle (arrow B direction). By this tensile force, the deep drawforming is performed for the blank material 14 in the width directionthat is approximately orthogonal to the vehicle direction, and thethree-dimensional shape can be formed from the second door opening part28 to the rear fender part 30 of the formed article.

Then, when the upper die 50 has reached a bottom dead center that is thelowest point of the upper die 50, the blank material 14 held between thelower die 48, the first and second blank holders 52, 54, and the upperdie 50 is formed into the formed article (side outer panel 12)corresponding to the shape of the cavity that is formed by the formingconcave part 58 and the forming convex part 60 that has entered theforming concave part 58.

After that, under the action of the lifting mechanism that is not shown,the upper die 50 is separated from the lower die 48 and the first andsecond blank holders 52, 54 to open the dies. Then, the formed articleis detached from the press forming device 10. Thus, the press formingfor the blank material 14 ends and the side outer panel 12 correspondingto the formed article is obtained. Note that when a trimming process isperformed for the formed article, the side outer panel 12 with the firstand second door opening parts 26, 28 opened is obtained.

As described above, in the present embodiment, in the press formingdevice 10 that performs the draw forming for the blank material 14including the first and second blank holes 32, 34, the first blankholder 52 is provided in the forming concave part 58 of the lower die 48and the second blank holder 54 with the circular shape is provided onthe outer peripheral side of the second holder part 66 of the firstblank holder 52 disposed on the vehicle rear side. The second blank hole34 includes the first and second opening parts 36, 38 whosecross-sectional shape is semicircular, and the pair of straight lineparts 40 a, 40 b that connects the first opening part 36 and the secondopening part 38. The pair of tension adjusting parts 42 a, 42 bextending to the inside of the second blank hole 34 is provided to thestraight line parts 40 a, 40 b.

Thus, when the draw forming is performed for the blank material 14, theupper die 50 and the first blank holder 52 hold the tension adjustingparts 42 a, 42 b, so that the bead 74 is formed. Therefore, the tensionapplied to the straight line parts 40 a, 40 b of the second blank hole34 outwardly can be adjusted as appropriate. In this case, even if theinflow of the blank material 14 in the front-rear direction of thevehicle (arrow A or B direction) is large, the tension is adjusted asappropriate, so that the convex part near the rear fender part 30 of theside outer panel 12 can be formed without wrinkles.

Moreover, the arched parts 44 a, 44 b of the first and second openingparts 36, 38 in the second blank hole 34 where the crack occurs easilyin the forming are set in advance such that the shape of the archedparts 44 a, 44 b is close to the shape of the formed arched part 46after the forming in the radial direction. Thus, it is possible tosuppress the inflow of the blank material 14 to the outside in theradial direction in the forming, so that the deformation amount(extending amount) after the forming is suppressed. Therefore, the crackcan be prevented as appropriate.

Furthermore, even if the extension is caused to the outside of thearched parts 44 a, 44 b in the radial direction as described above, thearched parts 44 a, 44 b is held securely between the upper die 50 andthe second blank holder 54 provided to the outer peripheral side of thefirst blank holder 52. Thus, the tension applied to the outside in theradial direction can be adjusted as appropriate without the bead.

In other words, even if the arched parts 44 a, 44 b of the first andsecond opening parts 36, 38 in the second blank hole 34 are enlarged indiameter so as to be positioned more on the outer peripheral side thanthe first blank holder 52, the forming can be performed in the statewhere the arched parts 44 a, 44 b are securely held by the second blankholder 54.

That is to say, when the press forming device 10 performs the drawforming for the blank material 14, the tension adjusting parts 42 a, 42b each including the bead 74 adjust as appropriate the tension appliedto the straight line parts 40 a, 40 b of the second blank hole 34outwardly. Also, the shape of the arched parts 44 a, 44 b is set so asto be close to the formed arched part 46 after the forming in the radialdirection. Thus, the crack can be prevented and the tension appliedoutwardly can be adjusted by holding the arched parts 44 a, 44 b by thesecond blank holder 54.

As a result, when the deep draw forming is performed for the blankmaterial 14 including the opening part, both the tension adjustment forthe straight line parts 40 a, 40 b and the tension adjustment for thearched parts 44 a, 44 b of the first and second opening parts 36, 38whose cross-section has the arched shape are performed as appropriate.Here, in the straight line parts 40 a, 40 b, a crack occurs less easilybut wrinkles occurs easily even if the inflow of the blank material 14is large, and in the arched parts 44 a, 44 b, the crack occurs easily ifthe inflow is large. Thus, even when the deep draw forming is performed,the crack does not occur at the second blank hole 34 of the blankmaterial 14 including the arched parts 44 a, 44 b and the straight lineparts 40 a, 40 b. For example, the deep draw forming is required in theside outer panel 12 (formed article) in the width direction of thevehicle from the second door opening part 28 to the rear fender part 30,and such side outer panel 12 for the automobile can be obtained thereby.

Note that the blank material, and the press forming method and the pressforming device for the blank material according to the present inventionare not limited to the above embodiment, and can employ variousstructures without departing from the gist of the present invention.

What is claim is:
 1. A blank material for which draw forming isperformed in a press forming device to make a body panel of anautomobile, the blank material comprising an opening part includingarched parts provided in an up-down direction of the body panel andconnection parts each having an approximately straight line shapeprovided in a front-rear direction of the body panel that isapproximately orthogonal to the arched parts and connected to the archedparts, wherein a tension adjusting part is provided to the connectionpart, the tension adjusting part extending to an inside of the openingpart and configured to adjust tension applied outwardly in forming. 2.The blank material according to claim 1, wherein the tension adjustingpart is formed for each of a pair of the connection parts.
 3. The blankmaterial according to claim 1 or 2, wherein each of the arched parts isformed in a manner that the arched part is smaller than a formed archedpart of a formed body in which the arched part has been formed, and thearched part has a shape that is close to the formed arched part.
 4. Apress forming method in which draw forming is performed for a blankmaterial including an opening part that includes arched parts andconnection parts each having an approximately straight line shape andconnected to the arched parts, wherein an edge of the opening part ispressurized and held between an upper die and a first blank holderprovided to a lower die, and the arched parts positioned outside a heldpart of the blank material held between the upper die and the firstblank holder is pressurized and held between the upper die and a secondblank holder provided outside the first blank holder.
 5. The pressforming method according to claim 4, wherein a bead is formed byholding, between the upper die and the first blank holder, a tensionadjusting part extending from the connection part to an inside of theopening part.
 6. A press forming device configured to perform drawforming for a blank material including an opening part that includesarched parts and connection parts each having an approximately straightline shape and connected to the arched parts, the press forming devicecomprising: an upper die; a lower die disposed so as to face the upperdie and including a mounting surface on which the blank material ismounted; a first blank holder disposed so as to face the upper die andconfigured to hold an edge of the opening part of the blank materialwith the upper die; and a second blank holder disposed outside the firstblank holder and configured to hold, between the second blank holder andthe upper die, the arched parts positioned outside a held part of theblank material held between the first blank holder and the upper die,wherein the first blank holder and the upper die include a beadconfigured to hold with pressure a tension adjusting part extending fromthe connection part of the blank material to an inside.
 7. The pressforming device according to claim 6, wherein the second blank holder hasa circular shape.
 8. The press forming device according to claim 6 or 7,wherein the bead extends along a direction that is approximatelyorthogonal to an extending direction of the tension adjusting part.